Order Of NH Research Articles

Nitrogen removal in subsurface constructed wetland: Assessment of the influence and prediction by data mining and machine learning

Subsurface constructed wetland (SCW) appears to be an economical and environmental-friendly practice to treat nitrogen-enriched (waste) water. Nevertheless, the removal mechanisms in SCW are complicated and rather time-consuming to conduct and assessment the efficiency of new experiments. This work mined data from literature and developed the machine learning models to elucidate the effect of influent inputs and predict ammonium removal rate (ARR) in SCW treatment. 755 sets and 11 attributes were applied in four modeled algorithms, including Random forest, Cubist, Support vector machines, and K-nearest neighbors. Six out of ten input features including ammonium (NH 4 ), total nitrogen (TN), hydraulic loading rate (HLR), the filter height (i.e., Height), aeration mode (i.e., Aeration), and types of inlet feeding (i.e., Feeding) have posed pronounced influences on the ARR. The Cubist algorithm appears the most optimal model showing the lowest RMSE i.e., 0.974 and the highest R 2 i.e., 0.957. The contribution of variables followed the order of NH 4 , HLR, TN, Aeration, Height and Feeding corresponding to 97, 93, 71, 49, 34, and 34%, respectively. The generalization ability to forecast ARR using testing data achieved the R 2 of 0.970 and the RMSE of 1.140 g/m 2 d, indicating that Cubist is a reliable tool for ARR prediction. User interface and web tool of final predictive model are provided to facilitate the application for designing and developing SCW system in real practice. • Four supervised ML algorithms were utilized to predict ARR by SCW. • Six over ten input variables were found to be the most pronounced parameters. • NH 4 -N (97%), HLR (93%), and TN (71%) contributed the most to model. • Cubist achieved the highest generalization with R 2 of 0.957 and RMSE of 0.974 g/m 2 d. • Strong correlation between the predicted and actual results by Cubist.

X-ray emission of z > 2.5 active galactic nuclei can be obscured by their host galaxies

We present a multiwavelength study of seven active galactic nuclei (AGN) at spectroscopic redshift >2.5 in the 7 Ms Chandra Deep Field South that were selected for their good far-infrared (FIR) and submillimeter (submm) detections. Our aim is to investigate the possibility that the obscuration observed in the X-rays can be produced by the interstellar medium (ISM) of the host galaxy. Based on the 7 Ms Chandra spectra, we measured obscuring column densities NH, X in excess of 7 × 1022 cm−2 and intrinsic X-ray luminosities LX > 1044 erg s−1 for our targets, as well as equivalent widths for the Fe Kα emission line EWrest ≳ 0.5−1 keV. We built the UV-to-FIR spectral energy distributions (SEDs) by using broadband photometry from the CANDELS and Herschel catalogs. By means of an SED decomposition technique, we derived stellar masses (M* ∼ 1011 M⊙), IR luminosities (LIR > 1012 L⊙), star formation rates (SFR ∼ 190−1680 M⊙ yr−1) and AGN bolometric luminosities (Lbol ∼ 1046 erg s−1) for our sample. We used an empirically calibrated relation between gas masses and FIR/submm luminosities and derived Mgas ∼ 0.8−5.4 × 1010 M⊙. High-resolution (0.3−0.7″) ALMA data (when available, CANDELS data otherwise) were used to estimate the galaxy size and hence the volume enclosing most of the ISM under simple geometrical assumptions. These measurements were then combined to derive the column density associated with the ISM of the host, which is on the order of NH, ISM ∼ 1023−24 cm−2. The comparison between the ISM column densities and those measured from the X-ray spectral analysis shows that they are similar. This suggests that at least at high redshift, significant absorption on kiloparsec scales by the dense ISM in the host likely adds to or substitutes that produced by circumnuclear gas on parsec scales (i.e., the torus of unified models). The lack of unobscured AGN among our ISM-rich targets supports this scenario.

Removal of nitrogen and phosphorus by heterotrophic nitrification-aerobic denitrification of a denitrifying phosphorus-accumulating bacterium Enterobacter cloacae HW-15

A new denitrifying phosphorus-accumulating bacterium HW-15 was screened out from phosphorus-rich wastewater and was identified as Enterobacter cloacae sp. based on its physiological-biochemical characteristics and 16S rDNA sequence analysis. The shift in microbial community structure during acclimation was determined through high-throughput sequencing and Enterobacter was found to be the dominant genus. Strain HW-15 exhibited efficient simultaneous denitrifying and phosphorus removal, and achieved both heterotrophic nitrification and aerobic denitrification process, and demonstrated a preference for consuming nitrogen sources in order of NH+ 4-N>NO- 3-N>NO- 2-N. The application of strain HW-15 in real wastewater samples resulted in NH+ 4-N, NO- 3-N, NO- 2-N and PO3- 4-P removal efficiencies of 99%, 88%, 59%, and 73%, respectively. Besides, strain HW-15 was found to simultaneously remove nutrient and arsenic(V) at an arsenic(V) concentration lower than 1.5mg/L. During anaerobic-aerobic culture period, the polyhydroxyalkanoate (PHA) content in HW-15 cells presented a dynamic change, and resulted in PO3- 4-P removal efficiency of 61.97%. Strain HW-15 could process NH+ 4-N to NO- 2-N and then to gaseous nitrogen.

Signal-Processing Interface for Inductive Displacement Sensor

In this paper, we present a signal processing interface for previously developed inductive displacement sensor, whose inductance is proportional to displacement of sensor elements. This measurement interface is based on measuring of root mean square (RMS) value of voltage on the sensor. This measurement method ensures good accuracy and high measurement rates of very small inductances, order of nH. A hardware realization of signal processing interface is described in details. Measurement results are presented and compared with values measured by impedance analyzer.

Measurements of key offensive odorants in a fishery industrial complex in Korea

Abstract This study was carried out to measure the concentrations of offensive odorants with an emphasis on nitrogenous compounds [NC: ammonia (NH 3 ) and trimethylamine (TMA)] and reduced sulfur compounds [RSC: hydrogen sulfide (H 2 S), methyl mercaptan (CH 3 SH), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS)] from various sources in a fishery industrial complex in Yeosu, Korea. Samples were collected from a total of 18 sampling sites including the major fishery facilities (C-1∼C-5) and the border areas (O-1∼O-8) of this fishery industrial complex during spring, summer, and fall. The mean concentrations of odorants at the major fishery facilities were found in the order of NH 3 (638 ppb), H 2 S (291 ppb), CH 3 SH (123 ppb), TMA (20.6 ppb), DMDS (7.71 ppb), and DMS (5.25 ppb). On the other hand, the mean concentrations of odorants at the border areas were NH 3 (85.3 ppb), TMA (1.75 ppb), H 2 S (0.25 ppb), CH 3 SH (0.18 ppb), DMS (0.07 ppb), and DMDS (0.06 ppb). The mean concentrations of H 2 S, CH 3 SH and TMA in the major fishery facilities greatly exceeded the Odorant Emission Guideline (OEG) applied to an industrial area. The concentration gradient of RSC between the major fishery facilities and border areas was more prominent than that of NC. From the correlation analyses, the highest correlation coefficient of 0.976 ( p = 3.99E−40, n = 60) was found between DMS and DMDS at the major fishery facilities, while NH 3 had a strong correlation with the sum of odorant concentrations (SOC) at the border areas ( r = 0.997, p = 4.83E−54, n = 48). The results of this study thus confirmed that CH 3 SH and TMA were the major odorants at the major fishery facilities and the border areas, respectively.

Use of kinetic models to explore the role of base promoters on Ru/MgO ammonia synthesis catalysts

The kinetics of ammonia synthesis over unpromoted and Cs-, Ba-, and La-promoted Ru/MgO (∼2 wt%) were studied in a tubular reactor at 20.7 atm. The reaction over all of the catalysts was nearly first order in N 2 and nearly zero order in NH 3. However, the order of reaction in H 2 was largely dependent on the choice of promoter, with Ba and La significantly reducing the inhibition by dihydrogen seen on Cs-promoted Ru/MgO. The turnover frequencies on Ba- and La-promoted Ru/MgO under stoichiometric conditions and 673 K were almost an order of magnitude greater than that on Cs-promoted Ru/MgO. Two kinetic models with optimized parameters were used to describe the outlet ammonia pressures determined experimentally both close to and far from equilibrium. Although Cs promotion of Ru lowered the activation barrier for N 2 dissociation, the enthalpy of dihydrogen adsorption and therefore the H atom surface coverage increased. Thus, promotion of Ru catalysts with bases cannot be attributed solely to an effect on dinitrogen dissociation, which is the rate-determining step. Base promotion is a trade-off between lowering the activation barrier for N 2 dissociation and increasing the competitive adsorption of H 2. The coverages of nitrogen-containing species determined by an optimized kinetic model matched well those determined experimentally by isotopic transient analysis over the same catalysts.

AFar Ultraviolet Spectroscopic ExplorerSurvey of Molecular Hydrogen in Intermediate‐Velocity Clouds in the Milky Way Halo

Far Ultraviolet Spectroscopic Explorer (FUSE) data are used to investigate the molecular hydrogen (H2) content of intermediate-velocity clouds (IVCs) in the lower halo of the Milky Way. We analyze interstellar absorption toward 56 (mostly extragalactic) background sources to study H2 absorption in the Lyman and Werner bands in 61 IVC components at H I column densities ≥1019 cm-2. For data with good signal-to-noise ratio (S/N) (~9 per resolution element and higher), H2 in IVC gas is convincingly detected in 14 cases at column densities varying between ~1014 and ~1017 cm-2. We find an additional 17 possible H2 detections in IVCs in FUSE spectra with lower S/N. The molecular hydrogen fractions, f, vary between 10-6 and 10-3, implying a dense, mostly neutral gas phase that is probably related to the cold neutral medium (CNM) in these clouds. If the H2 stays in formation-dissociation equilibrium, the CNM in these clouds can be characterized by compact (D ~ 0.1 pc) filaments with volume densities on the order of nH ~ 30 cm-3. The relatively high detection rate of H2 in IVC gas implies that the CNM in these clouds is ubiquitous. More dense regions with much higher molecular fractions may exist, but it would be difficult to detect them in absorption because of their small size.

NH 3 oxidation catalysed by calcined limestone—a kinetic study

The oxidation of NH 3 catalysed by calcined limestone was studied in a small fixed bed reactor at fluidized bed combustion temperatures (750–950 °C) using three types of limestones: Faxe Bryozo, Stevns Chalk and Ignaberga. It was shown that the limestones are very active catalysts for the oxidation of NH 3. Experiments were carried out with O 2 concentrations between 0 and 4.5 vol%. At low O 2 concentrations (<1 vol%), a strong increase in the NH 3 oxidation rate was observed with increasing O 2 concentration. At O 2 concentrations above 1 vol% no further effect of increasing the O 2 concentration was observed. The selectivity for NO formation found in most experiments is about 0.65–0.70 for all limestones used when the O 2 concentration is above 0.5 vol%. This means that the oxidation of NH 3 to NO is about two times faster than the oxidation to N 2. Below 0.5 vol% O 2, the selectivity for NO decreases with decreasing O 2 concentration. The selectivity for NO is not influenced by inlet concentrations of NH 3 or NO. The experimental observations are explained by a reaction scheme initially proposed by de Soete [Proc. of the 5th International Workshop on Nitrous Oxide Emissions, 1992] and modified in this study. The experiments showed that the NH 3 oxidation is first order in NH 3 and that the reaction rate is not influenced by NO. The influence of O 2 is modelled by a Langmuir model for O 2 adsorption on the CaO surface. Based on the kinetic model, reaction rate expressions for NH 3 oxidation to NO and N 2 were obtained from the experimental data. To our knowledge, this is the first time that validated reaction rate expressions, which can describe the NH 3 oxidation over calcined limestone over a broad O 2 range and a broad temperature range, are reported in the literature. The kinetics obtained in this work may be used to improve the modelling of NO emissions from fluidized bed combustors.

Processing and Functions of Hepatitis C Virus Proteins

Hepatitis C virus (HCV) has a positive-stranded RNA genome of about 9.5 kb and a large open reading frame encoding a precursor polyprotein of ca. 3,000 amino acids (aa). This polyprotein is cleaved by host cellular signalase(s) and viral proteases into 10 viral proteins in the order of NH₂-Core-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B-COOH. Core and E1/E2 are considered to be a capsid protein and envelope glycoproteins, respectively. NS2–NS5B are putative nonstructural proteins involved in the replication of HCV. NS2/3 is a metalloprotease which cleaves in cis at the NS2/3 junction. NS3 possesses serine protease and RNA helicase activities and is responsible for the cleavage of the remaining nonstructural proteins. NS4A is suggested to be a cofactor for NS3 protease. Although the function of p7, NS4B and NS5A are still unknown, an association of a mutation in NS5A with a susceptibility to interferon (IFN) has been reported. NS5B possesses an RNA-dependent RNA polymerase activity. Most of the current findings in HCV proteins depend on expression studies of HCV cDNA clones because of the lack of an efficient replication system in cell cultures. Therefore, a final assignment of cleavages and functions of HCV proteins has to await the propagation of HCV in cell cultures.

Electrochemical studies of the terminally substituted alkanethiol monolayers formed on a gold electrode: Effects of the terminal group on the redox responses of Fe(CN) 3−6, Ru(NH 3) 3+6 and ferrocenedimethanol

Self-assembled monolayers of the alkanethiols having OH, COOH and NH 2 terminal group were formed on a gold electrode via a sulfur attachment. The effects of their terminal groups on the redox responses of Fe(CN) 3− 6, Ru(NH 3) 3+ 6 and 1,1′-ferrocenedimethanol (FcDM 0) aqueous solutions were investigated by cyclic voltammetry. The voltammetric response of Fe(CN) 3− 6 was decreased in the order of NH 2 > OH > COOH terminal group. In contrast, the response of Ru(NH 3) 3+ 6 was increased in the order of NH 2 < OH < COOH. In the case of FcDM 0, the response was in the order of COOH > OH > NH 2. These results were discussed in relations to the effect of charged terminal group on (a) the shift of the potential drop across the diffuse layer and (b) the change of the concentration of redox species at the electrode surface which is caused by the electrostatic interaction between the terminal group and ionic redox species.

Modified activated carbons for the selective catalytic reduction of NO with NH 3

Activated carbons, modified with nitrogen- and oxygen-containing organic compounds by wet impregnation, followed by pyrolysis and CO 2 activation, have been used for the low temperature selective catalytic reduction (SCR) of NO with NH 3 (385–550 K). Of all the additives studied, only glucosamine results in an outstanding increase of the activity, which might be ascribed to the creation of stable surface oxygen complexes. These complexes can only be removed at relatively high temperatures and probably affect the carbon surface in such a way that adsorption of the reactants is improved, resulting in higher NO conversions compared to the original carbon. The explicit role of the incorporated nitrogen is not unequivocally clear. Apparently, the overall SCR activity is the result of a combination of the following factors: interaction of oxygen with the carbon, the presence of stable oxygen groups, the nitrogen content and the accessibility of the pores. For the modified carbons the SCR reaction is zeroth order in NH 3 and first order in NO. Furthermore, the oxygen dependency can be modelled by a Langmuir type of adsorption. Over the unmodified carbons a second type of selective NO reduction can be distinguished in which the carbon only acts as an adsorbents and for which a negative apparent activation energy is observed.

The catalytic reduction of nitric oxide by ammonia over a clean and vanadium oxide-coated platinum foil

The reduction of NO by NH3 could be readily monitored over a 2-cm 2 area platinum foil in the temperature range of 450–560 K. The reaction is first order in NO and zero order in NH 3 partial pressures, and the rate is given by r NO = 5 x 107 [NO] exp(- E/RT) (mol/cm 2.s) with E = 113 ± 20 kJ/mol. Vanadium oxide forms three-dimensional islands on Pt with a stoichiometry near V 20 4 . Its presence does not alter the activation energy appreciably but reduces the rate by blocking the active platinum sites.

Nitrogen recycling in coastal waters of southeastern U.S. during summer 1986

Summer-time pelagic nitrogen recycling using an {sup 15}NH{sub 4}{sup +} tracer technique was studied for important biological pathways, sinks, and residence times in the microbial food web of coastal Georgia, U.S.A. Results showed that estimated rates of NH{sub 4}{sup +} regeneration by a variety of microheterotrophs and microzooplankton balanced rates of NH{sub 4}{sup +} assimilation by the microbial community. In bottom water below the 1% light level, NH{sub 4}{sup +} regeneration exceeded community NH{sub 4}{sup +} assimilation by 3.5 times. However, over a period of 2 weeks, high NH{sub 4}{sup +} concentrations rarely occurred in bottom waters, and this was attributed to rapid mixing of the water column by winds and tides. Estimated mixing time from time-dependent numerical models were on the order of NH{sub 4}{sup +} turnover times of 5 to 10 hours. Overall, rates of community NH{sub 4}{sup +} assimilation exceeded rate estimates of phytoplankton N demand by 1.8 to 2.7 fold, which were made from rates of {sup 14}CO{sub 2} incorporation into proteins. In bottom samples where phytoplankton were light limited, rates of NH{sub 4}{sup +} assimilation exceeded the phytoplankton N demand by 3.6 to 11.1 fold. Calculations concerning the role of dissolved organic nitrogen in Nmore » cycling suggest that only 10% is recycled to NH{sub 4}{sup +} daily. This N could support 12 to 29% of the estimated phytoplankton N demand. Residence times of particulate nitrogen pools, based on rates of NH{sub 4}{sup +} regeneration, were on the order of 3-10 days. During summer-time hydrographic conditions and despite other losses, particulate nitrogen could recycle as often as 100 times before autumn removal processes occur off southeastern US.« less

Metastable Transitions II–V*–V in NH4NO3. I. Symmetry aspect and X-Ray Study at High Pressure

Crystallographical and group-theoretical analysis of the metastable phase transitions II–V * –V in NH 4 NO 3 is performed. The phase transitions are explained as a sequence D 4 h 5 (II)– D 2 h 13 (V * )– D 2 h 10 (V). The order parameter of the D 4 h 5 → D 2 h 13 phase transition transforms as the irreducible representation τ 3 +τ 3 * at the M -point of the Brillouin-zone boundary. The representation responsible for the transition D 2 h 13 → D 2 h 10 is τ 7 at the Z -point. It follows that II→V * is driven by an ordering of NO 3 - ions and V * →V is driven by an ordering of NH 4 + ions. With X-ray diffraction method, it is also found that the occurrence of the metastable transitions is facilitated by pressure. The temperature dependence of the intensity of superlattice reflection shows that the transition II→V * is of second order type and the critical temperature is 51°C at 0.15 GPa.

Photo-excitable membranes. Ion-selective photoresponse of poly(vinyl choloride)/spirobenzopyran membranes doped with nonactin and valinomycin.

The magnitude of the photoinduced membrane potential actoss poly(vinyl chloride)/spirobenzopyran membranes doped with nonactin or valinomycin depended considerably upon the kind and the concentration of alkali-metal and NH+4 cations in the aqueous solution adjacent to the ultraviolet (UV)-irradiated surface of the membrane. The photoresponse was suppressed with increasing concentration of the cations. The ion-selectivity in the potentiometric photoresponse of the nonactin-entrapped membrane was in the order of NH+4>K+>Rb+>Cs+>Na+>Li+, whereas the order of selectivity of Rb+>K+>Cs+>NH+4>Na+>Li+ was ovserved for the valinomycin-doped membrane. The results can be explained in terms of the binding abilities of nonactin and valinomycin for alkali-metal and NH+4 cations.

A quantum-chemical study of the chemisorption of ammonia, pyridine, formaldehyde, formate, and methoxy on ZnO(0001)

The chemisorption of ammonia, pyridine, formaldehyde, formate and methoxy on the Zn-terminated (0001) surface of zinc oxide is examined employing semiempirical quantum-chemical calculations (INDO/S) and a ZnO cluster of limited size (Zn 10O 10). The results indicate that upon adsorption on ZnO(0001), ammonia, pyridine and formaldehyde are moderate electron donors and that formate and methoxy are reasonably strong acceptors. H 2CO and C 5H 5N can be essentially considered as σ-donors, and HCOO is a σ-acceptor and a τ-donor. In the cases of ammonia, pyridine and formaldehyde, the contribution of the LUMO of the free molecule to the chemisorption bond is neglible. For the adsorption geometries examined here, it was found that the CH bond orders in C 5H 5N, H 2CO, HCOO and H 3CO, and the NH bond order in NH 3, are almost not affected upon adsorption. The chemisorption effects on the molecular orbitals and their energy positions are examined for all of the adsorbates studied. Based on these INDO/S results, the experimental UPS spectrum of NH 3 on ZnO(0001) is discussed. For each adsorbed molecule, charge transfers and dipole moments important to the change in work function are presented. Qualitative trends in the heat of adsorption of CO, H 2CO, NH 3 and HCOO on ZnO(0001) are discussed.

Synthesis of an intercalated compound of montmorillonite and 6-polyamide

Natural montmorillonite, fractionated from bentonite produced in Yamagata, Japan, was ion-exchanged for NH 3 + —(CH2)11—COOH, NH 3 + —(CH2)5—COOH, Al3+, Cu2+, Mg2+, Co2+, Li+, K+ and H+. The mixtures of the ion-exchanged montmorillonite and e-caprolactam were heated at 263 °C in glass ampoules for various periods. The intercalated compounds before and after the heating were examined by X-ray powder diffraction, DSC and GPC. Although e-caprolactam was not polymerized without montmorillonite, it was polymerized at 263 °C in the presence of montmorillonite. The polymerization rate varied with the interlayer cations in the order of NH 3 + —(CH2)11—COOH>Al3+>NH 3 + —(CH2)5—COOH>H+>Cu2+>Mg2+>Co2+>Li+>K+. After heating at 263 °C for 5 h, the mean number-average molecular weight was about 1.5 x 104. Although the interlayer distance of NH 3 + —(CH2)11—COOH type montmorillonite/e-caprolactam compound increased from 2.85 nm to 4.90 nm by heating at temperatures above the melting point of e-caprolactam, those of other compounds were not changed. After heating at 263 °C, an intercalated compound of montmorillonite and 6-polyamide, whose interlayer distance was more than 10 nm, was obtained. It is concluded that montmorillonite acts as a Bronsted acid and initiates the open ring polymerization of e-caprolactam and that the driving force of swelling is the polymerization energy.

Support and promoter effect of ruthenium catalyst. III. Kinetics of ammonia synthesis over various Ru catalysts

Ammonia synthesis over Ru powder, Ru/Al 2O 3, Ru-CsOH/Al 2O 3, Ru-CsOH, Ru/MgO, and Ru-CsOH/MgO was studied kinetically under 79 kPa (600 torr) at around 598 K. The kinetic expression was found to be affected markedly by the kind of support or promoter. The reaction order in N2 was unity for all the catalysts. However, the order in NH 3 was negative and that in H 2 was positive for Ru/Al 2O 3 and Ru/MgO, while the orders were near zero and negative respectively for other catalysts. It is discussed that N 2 adsorption is the rate determining step, and that the reaction is retarded by the different adsorbed species the nature of which depends upon the kind of support and promoter. It is suggested that the retarding species are both N (or NH) and H over Ru/Al 2O 3 and Ru/MgO, and H alone over Ru powder and CsOH promoted catalysts. Although promoted Ru catalysts are more active than iron catalysts at atmospheric pressure, the activity of the former would be exceeded by that of the latter at high pressure because of a hydrogen retardation.

Kinetics of the formation of N2O in the catalytic oxidation of NH3 on Pt-Rh filament

The kinetics of the reactions involving the formation of N2O in the catalytic oxidation of NH_3 have been studied over polyerystalline Pt-10% Rh filament in a static system, using a Fourier transform infrared spectrometer to monitor the partial pressures of NH_3 and N_2O. The formation of N_2O proceeds only over the filament temperatures range of 250～350℃. The reaction rate is of first order in NH_3 pressure and half order in O_3 pressure, and the rate equation can be written as v=k_(app)P_(NH_3)·P_(O_2)~(1/2). The apparent activation energy of the N_2O formation reaction from the temperature coefficient of the rate constants is found to be 25kcal/mol. The interpretation of these results in terms of Eley-Rideal type mechanism has been presented. The rate-controlling step might be the reaction between gaseous ammonia moleoules and the chemisorped oxygen atoms on the surface.

Differentiation and characterization of the cytoplasmic and nuclear deoxyribonucleic acid polymerases from baby hamster kidney cells

Distinct DNA polymerase activities have been found in the cytoplasmic and nuclear fractions of a baby hamster kidney cell line. They were separated by chromatography on DEAE-cellulose and partially purified by ammonium sulfate fractionation, DNA · cellulose and linear sucrose gradients. The cytoplasmic DNA polymerase exhibited an S-coefficient of 6.95 S in 0.15 M NaCl and its activity was highly sensitive to inhibition by N- ethylmaleimide and elevated temperatures, regardless of the presence of DNA template or other cofactors. It was stimulated by monovalent salts in the order of NH 4 Cl > KCl > NaCl > CsCI ⪢ LiCl (inhibitory). The DNA polymerase extracted from nuclei sedimented with an S-value of 3.47 S, was resistant to inactivation by N- ethylmaleimide , and maximally stimulated by NaCl, while also being inhibited by LiCl. For optimal activity, both DNA polymerase activities required a divalent cation, with MgCl 2 being more effective than MnCl 2. Although the optimal pH values for the two enzyme activities differed slightly, glycine · NaOH buffer induced an alkaline shift of 1.5 pH units in the optimum of both enzymes. This was accompanied by an increase in the effectiveness of MnCl 2 relative to MgCl 2 for the cytoplasmic DNA polymerase.